Influence of Angus and Belgian Blue bulls mated to Hereford x Brahman cows on growth, carcass traits, and longissimus steak shear force.

Steers and heifers were generated from Angus (A) and Belgian Blue (BB) sires mated to Brahman x Hereford (B x H) F(1) cows to characterize their growth, carcass traits, and LM shear force. A total of 120 B x H cows purchased from 2 herds and 35 bulls (14 A and 21 BB) produced calves during the 5-yr project. After the stocker phase, a representative sample of A- and BB-sired heifers and steers were transported to the Iberia Research Station to be fed a high-concentrate diet. The remaining cattle were transported to a commercial feedlot facility. Each pen of cattle from the commercial feedlot was slaughtered when it was estimated that heifers and steers had 10 mm of fat or greater. The BB-sired calves were heavier at birth (P < 0.01) than the A-sired calves. During the feedlot phase, the A-sired calves gained more BW (P < 0.05) than the BB-sired calves. The BB-sired calves had heavier (P < 0.01) carcass weights than the A-sired calves. This was due to a combination of a heavier final BW and greater dressing percent. Because of their greater muscling and reduced (P < 0.01) fat, carcasses from BB-sired calves had greater yield (P < 0.01) compared with carcasses from A-sired calves. Carcasses from A-sired calves had a greater (P < 0.01) marbling score and greater (P < 0.01) USDA quality grade than carcasses from BB-sired calves. Tenderness, as measured by shear force of the steaks aged for 7 d, was similar for A- and BB-sired calves. However, steaks aged for 14 d from the A-sired calves had a reduced shear force (P < 0.01) compared with steaks from the BB-sired calves. Steer calves were heavier (P < 0.01) at birth and weaning, and had more total BW gain in the feedlot, which resulted in a heavier final BW and HCW compared with the heifers. Steer carcasses also had greater marbling scores and quality grades, whereas the heifer carcasses had larger LM area per 100 kg of carcass weight. In conclusion, the BB-sired calves had heavier carcass weights and greater cutability, whereas the A-sired calves had a greater degree of marbling and greater quality grade, and steaks from carcasses of A-sired calves were more tender as measured by shear force at 14 d.

Effect of horn fly (Haematobia irritans) control on growth and reproduction of beef heifers.

The influence of horn fly control with commercially available ear tags was studied on beef replacement heifers (n = 670) for growth and reproductive performance. The study was conducted at five sites in Louisiana over 3 yr. Heifers used were yearling replacement females that were exposed to fertile bulls during a limited spring breeding season that coincided with the horn fly season. In mid to late May of each year, heifers were randomly assigned to one of two horn fly treatments: untreated and treated for horn fly control. The trial continued each year until September or October at the end of fly season. Pregnancy status was determined by rectal palpation. Horn fly populations were controlled on the treated heifers at moderate levels (84%). Total weight gain of treated heifers was 14% greater than for untreated heifers. Horn fly treatment had no effect on pregnancy rate (78% and 75% for untreated and treated heifers, respectively). Treatment differences for weight gain were of greater magnitude for heifers failing to conceive than for heifers that became pregnant. Weight gains of nonpregnant treated heifers were 33% greater than for nonpregnant untreated heifers, whereas weight gains of pregnant treated heifers were 8% greater than for pregnant untreated heifers. In conclusion, horn fly control on yearling beef replacement heifers improved weight gain but had no effect on first exposure reproduction.

Cow-calf and feedlot performances of Brahman-derivative breeds.

A study was conducted to compare Brangus, Beefmaster, Gelbray, and Simbrah breed influences for economically important traits. Brangus (9), Beefmaster (12), Gelbray (10), and Simbrah (7) sires were used in purebred and crossbred (Brahman x Hereford F1 cows) matings to generate calves (326) in eight breed groups. Beefmaster cows were of similar size (448 kg), Brangus and Gelbray cows were 11% heavier (501 and 503 kg), and Simbrah cows were 21% heavier (548 kg) compared to Brahman x Hereford F1 cows (452 kg). Calves sired by Brangus and Beefmaster bulls had lower birth weights (35 vs 38 kg; P < 0.05), preweaning growth rates (0.87 vs 0.91 kg x d(-1); P < 0.01), and weaning weights (206 vs 219 kg; P < 0.01) than Gelbray- and Simbrah-sired calves. Birth weights, preweaning ADG, and weaning weight and hip heights were similar between Brangus- and Beefmaster-sired calves. Simbrah-sired calves had greater preweaning growth rates (0.94 vs 0.88 kg x d(-1); P < 0.05), weaning weights (227 vs 211 kg; P < 0.01), and adjusted 205-d hip heights (126 vs 122 cm; P < 0.05) than Gelbray-sired calves. Straightbred Angus steers were introduced in the postweaning portion of the study. Steer calves were placed on feed at an average age of 14.5 mo. Steers were removed from the feedlot upon attaining a targeted 10 mm of backfat. Feedlot ADG did not differ among sire breeds. Brahman-derivative sired steers required an additional 54 d on feed (P < 0.01) and were 86 kg heavier (P < 0.01) at harvest than Angus steers. Continental-Brahman steers spent an additional 25 d on feed (P < 0.05) and were 35 kg heavier (P < 0.01) at harvest than British-Brahman steers. Simbrah-sired steers were 52 kg heavier (P < 0.01) at harvest than Gelbray-sired steers when fed for a similar number of days (211 vs 203 d). However, straightbred Simbrah steers required an additional 12 d on feed (P < 0.01) and weighed 47 kg more (P < 0.01) than Simbrah-sired crossbred steers. The economic value of the heavier calf weaning weights may be offset by the attendant larger cow size of the Continental-Brahman compared to the British-Brahman breeds. Similarly, the heavier weights of Continental-Brahman compared to British-Brahman steers, when harvested at a prescribed level of fatness may be viewed as a benefit, but the increased number of requisite days in the feedlot is a disadvantage.

Influence of permethrin, diazinon and ivermectin treatments on insecticide resistance in the horn fly (Diptera: Muscidae).

The history of insecticide resistance in the horn fly, Haematobia irritans, and the relationship between the characteristics of horn fly biology and insecticide use on resistance development is discussed. Colonies of susceptible horn flies were selected for resistance with six insecticide treatment regimens: continuous single use of permethrin, diazinon and ivermectin: permethrin-diazinon (1:2) mixture; and permethrin-diazinon and permethrin-ivermectin rotation (4-month cycle). Under laboratory conditions, resistance developed during generations 21, 31 and 30 to permethrin, diazinon and ivermectin, respectively. The magnitude of resistance ranged from < 3-fold with ivermectin to 1470-fold with permethrin. Field studies demonstrated that use of a single class of insecticidal ear tag during the horn-fly season resulted in product failure within 3-4 years for pyrethroids and organophosphates, respectively. In laboratory studies, use of alternating insecticides or a mixture of insecticides delayed the onset of resistance for up to 12 generations and reduced the magnitude of pyrethroid resistance. In field studies, yearly alternated use of pyrethroids and organophosphates did not slow or reverse pyrethroid resistance (Barros et al., unpublished data), while a 2-year alternated use with organophosphates resulted in partial reversion of pyrethroid resistance. When pyrethroid and organophosphate ear tags were used in a mosaic strategy at two different locations, efficacy of products did not change during a 3-year period.

Performance of Angus and Brangus cow-calf pairs grazing Alicia bermudagrass and common bermudagrass-dallisgrass pastures.

This research was designed to examine genotype x environment interactions in cow-calf growth performance of grazing animals. Angus and Brangus cow-calf pairs (minimum of six per breed) were allowed to rotationally graze (14-d intervals) treatment pastures from approximately May through early October in each of 2 yr. Treatment pastures contained relatively pure stands of Alicia bermudagrass (AP) or a mixed stand of common bermudagrass and dallisgrass (CDP). Forage allowance was equalized, using "put-and-take" cow-calf pairs, among forage and breed types at the initiation of each 14-d grazing interval. Forage samples were obtained in each paddock at the initiation of each grazing interval. Forage CP concentration was greater (P < .05; 13.5 vs 11.6%) and NDF concentration was less (P < .05; 63.8 vs 70.6%) for CDP than for AP. Daily weight loss was similar for Angus and Brangus cows, but it was greater (P < .05) for cows grazing AP than for cows grazing CDP. Calf ADG during the grazing season was 35% greater (P < .05) for CDP than for AP pastures and was 23% greater (P < .01) for Brangus than for Angus calves. Relative performance of Angus and Brangus cow-calf pairs was consistent between forages; no breed x forage interactions were observed.

Monensin and ammoniation or urea supplementation of bermudagrass hay diets for steers.

One growth trial using crossbred beef steers (297 +/- 2 kg, Exp. 1) and one metabolism trial using Holstein steers (405 +/- 14 kg, Exp. 2) were conducted to evaluate effects of ammoniation (3% of hay DM, added as anhydrous NH3) vs urea supplementation with or without monensin supplementation of mature 'Alicia' bermudagrass hay-based diets for steers. Ammoniation (P < .05), but not urea (P = .26) or monensin (P = .70) supplementation, increased ADG in Exp. 1. In Exp. 2 ammoniation increased hay DMI (P < .05), but urea (P = .88) or monensin (P = .16) had no effect. Supplementation with either monensin (P < .05) or urea (P < .05) decreased ruminal total VFA concentrations. Monensin also decreased the ruminal acetate:propionate ratio (P < .001) and increased ruminal pH (P < .05). Addition of urea to the concentrate supplement decreased the rate of concentrate intake. Both the rate (P < .05) and the potential extent (P < .001) of ruminal forage in situ DM and NDF disappearance were increased by ammonia treatment. Dietary interactions (P < .10) were detected between monensin and ammoniation for rate and potential extent of in situ NDF disappearance and between monensin and urea supplementation (P < .05) for ruminal total free amino acid concentrations. Decreased concentrations of VFA and lower forage digestibilities observed with monensin supplementation in Exp. 2 may explain the failure of monensin to affect ADG in Exp. 1.

Prepartum body condition and weight influences on reproductive performance of first-calf beef cows.

Data were collected on 476 spring-calving, primiparous cows at six locations in Louisiana over a 2-yr period. Objectives of the study were to evaluate changes in prepartum body condition score (BCS) and BW of heifers when fed varying energy levels and to determine the influences of prepartum BCS and BW changes and BCS at calving on postpartum traits. Heifers were allocated to one of three energy levels from approximately 90 d prepartum to parturition. The diets were formulated to provide low, recommended, and high energy levels based on TDN requirements. After calving, cows were placed on annual ryegrass pasture and managed similarly at each location. Weight and BCS at calving were greater (P < .05) for females with higher BCS at 90 d prepartum (IBCS) and for those assigned to higher energy levels. Calving and calf growth traits were not affected (P > .05) by IBCS, energy level, prepartum changes in BCS and BW, or BCS at calving. Prepartum changes in BCS and BW regulated by varying energy levels had no effect (P > .05) on postpartum reproduction; however, BCS at calving influenced (P < .03) pregnancy rate and days to pregnancy. Cows with BCS 6 and 7 at calving had higher (P < .05) pregnancy rates (87.0 and 90.7%) than those with BCS 4 and 5 (64.9 and 71.4%). Interval to pregnancy for cows with BCS 4 at calving was 10 to 18 d longer (P < .05) than for those with BCS > or = 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of supplemental lysocellin and tetronasin on growth, ruminal and blood metabolites, and ruminal proteolytic activity in steers grazing ryegrass.

Forty-eight Angus and Brangus steers (249 kg initial BW) were used in a randomized complete block design. Steers grazed annual ryegrass (Lolium multiflorum [L.] Lam.) for 107 d and were sampled at 35 and 70 d. Treatments consisted of a corn supplement (C) or corn supplement plus either 80 mg.steer-1.d-1 of lysocellin (L) or 60 mg.steer-1.d-1 of tetronasin (T). When compared with C, ADG of L- and T-fed steers was higher (P less than .05) for the complete 107-d study (1.15 vs 1.25 kg/d). At 35 d, ruminal acetate:propionate ratio tended (P = .07) to be higher for C than for L- and T-fed steers (4.6 vs 3.8). When compared with T, steers fed L tended (P = .11) to have higher acetate:propionate ratios. Ruminal concentrations of ammonia and free amino acids were not affected (P greater than .05) by treatment, but ruminal proteolytic activity tended (P = .13) to be lower for L- and T-fed than for C steers at 70 d. Ionophores did not alter (P greater than .05) ruminal mineral concentrations, but ruminal Mg concentration tended (P = .14) to be higher for T- than for L-fed steers at 70 d. When compared with L- and T-fed steers, C steers had lower (P less than .05) plasma concentrations of Mg (23.7 vs 21.9 mg/liter) and Ca (113.0 vs 104.2 mg/liter) at 35 d. Plasma mineral concentrations were similar (P greater than .05) for L- and T-fed steers. Data are interpreted to indicate that L and T may improve ADG, decrease ruminal acetate:propionate ratio, and alter mineral metabolism.

Effects of breed and wintering diet on heifer postweaning growth and development.

Fifteen spring-born Angus (AN) and 25 Brangus (BN) weanling heifers were used in a 2x5 factorial arrangement of treatments to evaluate the effects of breed and postweaning winter diet on heifer growth and development. Dietary treatments were warm-season perennial grass hay (H), ammoniated H (AH), H plus .68 kg/d cottonseed meal (HP), H plus .45 kg/d cottonseed meal plus 1.37 kg/d ground corn (HPE) and HPE plus 200 mg/d monensin (HPEM). Mean initial weight and age for the 107-d feed trial were 207 kg and 270 d. Brangus had .06 kg greater (P less than .05) ADG than AN during the trial. Although digestible DM intake (DDMI) relative to body weight was greater (P less than .10) for AN than for BN, ADG:DDMI was greater (P less than .05) for BN than for AN. Heifers fed H and AH lost weight, but heifers fed AH had 50% (P less than .05) less daily weight loss than those fed H. Daily gain increased (P less than .05) incrementally in response to sequential supplement additions of cottonseed meal (AH vs HP; -.10 vs .17 kg), ground corn (HP vs HPE; .17 vs .29 kg) and monensin (HPE vs HPEM; .29 vs .39 kg). Hay DM intake relative to body weight and DDMI were increased (P less than .01) by ammoniation. Intake did not differ between HPE and HPEM. Diet affected age at puberty (P less than .05), which decreased with increased dietary components. Weight differences among diet groups following the winter feed trial were largely eliminated prior to breeding. Nevertheless, H- and AH-fed heifers collectively weighed less (P less than .01) prior to breeding than did heifers of supplemented diet groups. Reproductive development tended to be adversely affected by weight loss during the postweaning period.

Dose-response relationship of tetronasin administered to grazing steers.

Two grazing experiments were conducted to evaluate the dose-response relationship of steers to the ionophore tetronasin. Bermudagrass-based pastures were grazed 126 d in Exp. 1, and annual ryegrass or an annual ryegrass-berseem clover mixture was grazed 112 d in Exp. 2. Tetronasin was administered in ground corn (.91 kg/hd) fed daily to provide dosages of 0, 7.5, 15, 30, 60 or 90 mg. One hundred forty-four steers (220 kg, Exp. 1; 196 kg, Exp. 2) were allocated to treatment groups of six steers within four initial weight blocks in Exp. 1 and within two initial weight blocks, assigned to two forage types in Exp. 2. Initial weight blocks were confounded with four pasture blocks, divided in six 1.35-ha paddocks. Treatment groups were rotated among paddocks within pasture block every 2 wk. Stepwise tetronasin addition resulted in a linear increase (P less than .05) in the proportion of propionic acid and a linear decrease (P less than .05) in the proportion of acetic acid and the acetic to propionic acid ratio in both experiments. Total VFA concentrations were not altered in Exp. 1 but they decreased linearly in Exp. 2 with tetronasin addition. Maximal observed improvement in daily gain (.1 kg) occurred at a dosage of 30 mg.hd-1.d-1 in Exp. 1 and 90 mg.hd-1.d-1 in Exp. 2. Daily gain increased linearly (P less than .06) with tetronasin level in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of breed and wintering diet on growth, puberty and plasma concentrations of growth hormone and insulin-like growth factor 1 in heifers.

Twenty-five Brangus (BR) and 15 Angus (AN) heifers were used to study the effects of breed and wintering diet on average daily gain (ADG), onset of puberty and plasma concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Wintering diets (fed for 107 days beginning November 15) consisted of the following: 1) native grass hay (NGH), 2) ammoniated NGH, 3) NGH plus cottonseed meal, 4) Diet 3 plus corn and 5) Diet 4 plus monensin. After wintering, heifers were transferred to ryegrass pasture for 70 days. Mean ADG during the wintering phase were -.20, -.10, .17, .29 and .39 kg for heifers fed Diets 1 through 5, respectively (P less than .01). ADG was greater (P less than .05) for BR than for AN heifers. Plasma concentrations of GH were higher (P less than .05) in heifers fed Diets 1 and 2 than in heifers fed Diets 3, 4 or 5. Plasma concentrations of IGF-1 were lowest in heifers fed Diet 1 and highest in heifers fed Diets 4 and 5. During ryegrass grazing, GH concentrations were similar for all groups. However, concentrations of IGF-1 were higher (P less than .05) in heifers fed Diets 3, 4 and 5 than in heifers fed Diets 1 and 2. Age at puberty (onset of cyclic progesterone concentrations) was greatest in heifers fed Diet 1 and lowest in heifers fed Diet 5. Weight at puberty was not affected (P greater than .10) by wintering diet but was greater (P less than .01) in BR than in AN heifers. Therefore, negative ADG appears to be associated with elevated plasma GH concentrations in heifers, and plasma IGF-1 concentration appears to be a more accurate indication of nutritional status than plasma concentrations of GH.

Preventing adverse effects on the temporomandibular joint through orthodontic treatment.

The temporomandibular joint is one of the most complicated working assemblies in the human body. We are just now beginning to understand it and give it the respect and careful treatment it deserves as an integral functioning part of the dental anatomy. No orthodontic procedure can be performed in isolation without considering its possible effect on the temporomandibular joint. Therefore, the following recommendations are made for diagnosis and treatment planning. Etiologic factors that might cause upward and backward pressures on the mandible should be reduced as much as possible. Mechanotherapy that may cause upward and backward pressures on the condyles is not recommended. Final detailed correction of dental abnormalities should always consider optimal temporomandibular health and function. Retention procedures should be planned to provide a proper path of closure to minimize or prevent possible retrogressive posttreatment changes. It is the author's hope that the hypotheses and suggestions in on TMJ problems and on the preventive role of orthodontics in the patient's treatment.